Building a slipform wall on a post frame home?

Jake Milner

Posts: 8

posted 1 year ago

Hi

I have researched as far as my eye can see. But just cannot find the exact information I am looking for.

We decided to build a DIY post frame home. We have very rocky, sandy soil. And our building pad is nice and level, setting halfway down a hillside. So drainage is excellent already. I believe the frost line in our level is 2 to 3 feet. Anyway. The home will be 24x36 using 6x6 treated posts, set 4ft in the ground on top of poured footers. The thing is. My wife wants me to do a slipform exterior wall around the house. I have no problem with this. Except I am not sure how to put footings in the ground to support it. Since there will undoubtedly be posts in there as well. The post footings will be 5ft down. Which is overkill for a slipform wall that isn't supporting anything. For the record, I am also planning to erect either a slipform or dry stack block for the interior wall. Both in and out walls with have R20 sheet insulation in between. And both will need the footings. I also plan to pour a floating slab. Which will be insulated underneath and around.

So the question is easy. How do I plan the make this all work? Getting the posts in the ground. Getting footings down and wide enough for interior and exterior slipform walls. And keep it all separate for a floating slab?

Thanks!

Simon Malik

Posts: 25

Location: Cincinnati, Ohio

1

posted 4 months ago

My first post folks, after lurking in this wonderful place for a while.

I actually have a very similar idea in mind. I've been turning something very similar over in my head. Except I want to do it on an already existing stick/frame house, with a stone foundation.

Basically what I've been obsessing over is the idea of digging a trench around the whole existing foundation, below the frost line, drill some holes for rebar into the existing exterior foundation, tie the rebar frame that I put in the foundation ditch to the existing foundation, pour a concrete fooder in this trench, and then just slip-form up the side essentially using the exterior walls of the frame house as a frame, worst case stripping its siding off and going against the sheeting, insulating and patching as I go.

Now to get even weirder, I was thinking of using lime concrete instead of portland cement based concrete. "Limecrete" in essence. Traditional lime mortar with pebbles and rock chunks as aggregate for strength.

The reason is for breathibility and that there's less embedded energy in the production of lime vs cement, so it feels like a better more natural solution to me.

Is there anyone out there who can offer advice, tell me this idea is insane don't do it, or tell a story of someone you've observed doing something very similar, and how it worked out?

Thanks !

andre hirsz

Posts: 43

Location: thunder bay ontario canada

1

posted 3 months ago

1

I'm looking at building a similar model using 2 ft wide slipform on ground level, up 3 ft to floor joists. Slipform wall to rest on gabion wall below grade, down to cement footer. With sono tubes every 6 ft through the gabion wall. Slipform wall rests on gabion wall and sono tubes. look up gabion wall construction.

Alan Loy

Posts: 66

Location: Melbourne Australia

3

posted 3 months ago

2

Once you get away from the ground I wonder how "slip form" with stones and cob would work. Perhaps ramming it a bit to give the advantages of rammed earth construction.

Maybe I'm combining to many techniques but I keep being reminded of Dhajji Dewari that works well in Pakistan and surrounding ares It combines stone, cob and timber framing.

Hi Alan. I love working with cob but in a northern climate , am hesitant of snow build up on outdoor cob structures. And I'm not sure if gabions alone without mortar wouldn't settle. So I'm looking to place sono tubes to footer below frost line. My plan for the footing is in an oval or racetrack oval for further strength. My floor will be in a rectangle sitting on the oval foundation.

Alan Loy

Posts: 66

Location: Melbourne Australia

3

posted 3 months ago

2

As I live in Oz I forget about people living where the water gets hard BUT I imagine that northern Pakistan and parts surrounding get pretty cold. I'm afraid I don't know how it would stand up to frozen winter conditions.

from the World housing encyclopedia
Dhajji Dewari is a timber frame with stone and earth infill, typically used in the mountain regions of South Asia. Similar construction is used around the world, under different names. Himis is a Turkish variation, used to help reconstruct after their 1999 earthquake. In Portugal, builders have used Gaiola Pombalina since a 1755 Lisbon earthquake rocked the city. Lastly, Italy uses Casa Baraccata another timber frame, stone infill construction.

andre hirsz

Posts: 43

Location: thunder bay ontario canada

1

posted 3 months ago

Ahhh with this new info I see that the conditions would require a much different design. And things like exterior cob properly designed could work.

Simon Malik

Posts: 25

Location: Cincinnati, Ohio

1

posted 2 months ago

1

Alan, Andre, interesting thoughts on Dhajji Dewari and Cob.

Here's an update to this thread, and it makes me wonder if I mentally overcomplicate things. I've been doing a bit of reading in older sources, it seems what the early 20th cent architect who came up with the idea of slipform stone masonry for small houses, Ernest Flagg, was actually doing was something like this. His forms were framed wall high, if I'm understanding what I read correctly.

So, I'm growing obsessed by this... And when I get obsessed by an idea I dig and I dig. The other day I was digging around and stumbled on an old WPA era Rock House Building pamphlet that cites an established rural practice that looks like a precursor to contemporary slipform masonry using cobblestone rocks.

I did some other searches and came across some interesting things that suggest Earnest Flagg, whose technique inspired the Nearings, may have been inspired by this technique from vernacular builders. In any case it seems to have once been common in the Ozarks.

You use a wood-fame house wall as a backing form, and basically build a rubble or cobblestone wall with concrete mortar and ugly rocks embedded in it behind.

Or you have a slipform framed with some planks secured by poles in back, but the front is open, and you slip the backing boards up as you go, just like in current Slipform Stone Masonry, but the front is open.

So I dug around some more and found some early 19th century agricultural building references, doing silos and barns, with a similar technique but this time with a two sided boxed slipform, you firmly plant "standards" thick wood poles, then put the planks behind at the right distance, and properly braced throw in a layer of mortar, dump cobble stones or rocks, throw some more mortar or concrete, tamp or ram it down, repeat moving the forms up.

I suspect slipform Stone masonry, much less than slipform concrete, is older than many of us would imagine.

I read his links, and then dug around some more in old references, it seems the idea of using slip forms and ramming the concrete and aggregate was an essential part of this technique, and taken from older rammed earth, pise-de-tere or Tapia practices.

Now Roman concrete also was rammed in formworks, with large aggregate.. 2000 years ago.

It makes me wonder where else similar techniques have popped up, and for how long..

Fascinating !

Simon Malik

Posts: 25

Location: Cincinnati, Ohio

1

posted 2 months ago

2

Here are some philosophical thoughts expressing some of my anxieties, as I plan a humble house for my wife and I.. thinking of broader ramifications.

Buildings and civilization have always fascinated me, since childhood. Masonry, as opposed to timber, has an emotional resonance for me. One of permanence, solidity.

Earthen architecture echos this. But thinking about cob, vs lime and cement, and my attraction to concrete and stone, one of the things that concerns me is sustainable permanence.

So I'm torn a bit. Cob can be long lasting, but depending on climate it, like rammed earth, needs wise maintenance over the years to prevent water damage and erosion.

Portland cement based concrete and lime both contain a lot of embedded energy, and our civilization seems addicted to unsustainable levels of concrete production.

But what if the sustained social use of buildings built with concrete or lime - in particular utilizing products like fly ash - were such that it offset the initial energy spent manufacturing and transporting it, the carbon produced, and the shorter term ecological consequences?

Everywhere in developed older civilizations buildings, whether private or public, could continue giving use for centuries after their construction. Maybe the problem with our use of concrete in North America, particularly, and the rest of the developed world, was simply mindset. That we don't intend, in many cultures, to build to last.

What if our stone masonry, concrete, and brick works were done with the intention and will to last for generations? Would that in itself not be "Green"?

andre hirsz

Posts: 43

Location: thunder bay ontario canada

1

posted 2 months ago

Wow thank you Simon. Would not of occurred to me to use 2 forms rather than 3 for slipform construction. This would also simplify the placement of pipes or windows through the wall for light and airflow or other utilities...water , electricity. Will work beautifully for the design I have in mind for a model of a small self sustainable unit. Thanks again.

I'm reading up on the history of slipform stone masonry because I'm looking for tips and tidbits of information on how people dealt with issues and problems, in earlier times with fewer technological resources available. I'm hoping it expands my mind on what's possible, and how things could be done in a more sustainable way, in a cheaper way, in a way with lower impact.

That booklet above really opened my eyes. It seems that slipform stone masonry became really popular in Missouri, and through the Ozarks, between 1910 and the 1940s. I dug around and there were a few other booklets like that floating around but I have yet to locate copies.

A couple of more things. There's a bit more about this in the government's Ozark Native Stone buildings surveys that interviewed homeowners and builders. The other pdf links documents a bit of this, and there's some more info floating around the net on "Ozark rock masonry" and especially using slipforms before the 1940s..

I'm reading up more on all of this to sort of glean more tidbits of information and techniques. Either practical stuff or inspirational stuff, seeing how people solved basic problems creatively. It might help inspire me into a more creative way of thinking.

Something that's really occurring to me as I - basically - geek out reading up on this stuff is that there are many, many, ways of solving basic building problems in a low tech and low impact but effective way. Albeit with a lot of elbow grease...

Something that really fascinated me about Permacuture in general was that if we look through history across the world we can see that people did many things, in different places, that worked well for where they were and what their situation was (though not always) and that today we can be inspired by a technique someone did, or a more holistic look at their whole context, and be inspired by it in finding low-impact and sustainable ways to do things with our existing technology and body of knowledge today. Just because someone did something in their indigenous situation 500 years ago and it worked for them doesn't mean that there's not a more effective way of solving a similar problem now.. but their creative processes and experiences can teach us.

So anyway I'm geeking out here, cramming my brain reading about what appears to be a really old way of building. And one that's far more widespread than I thought. For example, It seems that some early 20th century urban stone masonry buildings in Palestine were build in a similar way, concrete backing or core walls partially wood formed, and stone facing. I;m still digging up references to see exactly how some concrete and stone (possibly lime mortar based concrete) wood-formed stone buildings were done in the West Bank, for example. Or, and I'll get into this, flint masonry churches and houses in Northern England..

I've sometimes seen it mentioned that Slipform stone masonry was started by, or picked up because of the architect Ernest Flagg, but I've seen mentions that a lot of people in the Ozarks got turned onto stone building because of the Craftsman movement, and in particular reading Craftsman magazine. I can't find copies yet but I'm sure there's something out there interesting.

Helen Nearing is supposed to have learned of it from Ernest Flagg's books. But there was another architect who encouraged a more DIY attitude than Flagg did, and modifying some of Flagg's methods. Frazier Forman Peters.

Frazier Forman Peters build several well known homes, and advocated people use similar techniques in doing either stone faced wood-form backed houses with or full concrete houses.

Frazier Forman Peters wrote a couple of interesting but really hard to get books about DIY house building. One is "Pour yourself a house: low-cost building with concrete and stone". I couldn't find a PDF anywhere and print copies are $75 on Amazon, but it is listed in OpenLibrary.org for electronic checkout.

He also wrote "Houses of stone." (1933) which does have a pdf on archive.org

Digging around though I found some earlier stuff, that made me think Ernest Flagg got his techniques from stuff people were already doing. For example, lookup "gravel-wall" construction.

Basically people were using slipforms to do lime mortar and gravel concrete houses poured in 1 foot lifts. They'd let it set a few days, then move the forms up.

At the same time there were other masons in the 1800s doing cobblestone masonry houses. There's little published about how they did it, but there's some suggestions I ran into that some of them may have used movable wooden forms.

Then I started digging around and found some old farm magazines from around the civil war or before in which people were doing the exact same thing, using planks as slipforms, set in front of poles that they called "standards" and building barns or utility buildings in 1 foot lifts by throwing down lime mortar or concrete, dumping rocks or cobblestones in it, and then raising it etc.

Now, it turns out, the Cobblestone masonry builders were quite possibly influenced by flint cobblestone builders in England. In Norwich, for example, practically the whole old town, everything pre-20th century, is built of little fist size cobblestones. Well, it turns out, some of these buildings going back to the middle ages were built using a sort of "movable timber shuttering" and medieval drawings of workmen show the use of "movable shuttering" - slipforms essentially - very similar to the ones illustrated in that Ozarks booklet or that Ernest Flagg used..

I'll dig up the source, but one book I saw mentioned that medieval flint masonry builders built in 1 foot tall lifts, roughly, throwing down a bed of lime mortar and throwing the stones in, carefully working the edges, but the middle was full of just random ugly stones.

They let it cure, lifted the boards up another foot, repeated etc.

They built entire cathedrals that way.

John C Daley

Posts: 44

Location: Bendigo , Australia

1

posted 1 month ago

1

I build all the time with different materials.
I have read all those entires on this topic and have come to a occlusion that most of the trouble you get into arises because of incorrect terminology.
I get this in Australia and it creates all sorts of issues until somebody points it out.
I am glad Simon worked out that 'slip forms' actually slip.
Almost any medium can be placed within the slipform formwork, which is moved when things have dried, set etc.

Going back to the original entry, I will use the terms as I see them and see if it is clearer.
Post and beam may the style intended with posts set into the ground and beams across the top to hold a roof or a second storey.
The walls between the posts we would call infill panels and may be a variety of materials which may also envelop the posts in the process.
Foundations are called footings in some cases.

The advantage of post and beam is that a roof can be put up before the walls are complete and you have a dry, shady place to work.
Cob is called mud brick in Australia, being made for soil which may have straw added and then set into moulds or presses, dries hard and then are laid as clay fired bricks may be laid.
Cob is usually, an English term for damp soil lifted from the ground and placed directly in position to form a wall and left to dry before more is added.

The best way for installing posts, is to drill the soil, drop the post in and back fill with concrete.
Its best to leave the hole open at the bottom so water does not get trapped in the column and rot the posts. Here that can be an issue.

I always recommend steel posts, because they do not rot nor rust if used correctly, are much lighter and often easier to get now.

In Jakes case the post holes may go down the 5 feet he needs, then the soil for the wall footings can be excavated to the depth required by the wall design, I image about 2 feet to firm ground.
Once the footings are poured with concrete the walls can commence.
Limecrete has many advantages over portland cement concrete, but its harder to get supplied.

I have heard that its great for patios etc because it does not hold nor reflect as much heat as conventional concrete does.
In Australia, the reflected heat from concrete slabs is a problem.
Anyway, I hope I have helped some of you.

Cob is called mud brick in Australia, being made for soil which may have straw added and then set into moulds or presses, dries hard and then are laid as clay fired bricks may be laid.

Cob is defined as a mixture of clay, soil, sand and straw, wetted and mixed then formed into balls (cobs) and pressed into place to form a wall.

Mud brick is what the Egyptians used and in the USA it is called Adobe, it is a mix similar to cob but it is pressed into a form and left to dry then used just like "Bricks" (stacked in an offset manner to create stability).
There is usually some form of "mortar" used such as clay slip or a looser form of the brick mixture that has the straw left out.

Terminology is all important when different parts of the world start talking about construction materials and methods.